Iontophoresis has been utilized for many years for delivering medication into the body of a patient to diagnose and treat various ailments. Another related procedure iontohydrokinesis has been proposed for similar use. For example, iontophoresis has been utilized to deliver Pilocarpine medication to diagnose cystic fibrosis, for the permeation of insulin through the skin, the introduction of steroids into joints to treat arthritis, to anesthetize the eardrum or eye, to treat plantar warts with sodium salicylate, to treat canker sores in the mouth with steroids, to treat Peyronie's disease (the fibrosing of the penis), and to deliver procainamide across the heart during experimental open chest surgery in dogs.
Iontophoresis involves the transportation of medication in the form of naturally charged or ionic molecules by creating an electric field which acts as a driving force to cause the molecules to advance toward an oppositely charged pole. More particularly, iontophoresis is defined in Steadman's Medical Dictionary as the introduction by means of electric current of ions of soluble salts into the tissues of the body for therapeutic purposes; alternatively, the facilitated entry of electrically charged drugs into the surface tissue by application of an electric current. For example, if fluid having charged molecules is placed on a patient's skin and a properly oriented electric field is developed, the fluid will permeate the patient's skin. Where the molecules normally are uncharged, they may be rendered ionic by lowering or raising the pH of the carrying fluid.
The principle is similar for iontohydrokinesis which may be used to deliver uncharged, non-polar molecules of medication. In iontohydrokinesis, water, which has naturally charged molecules and containing noncharged or non-polar molecules of medication, is transported into the tissue of a patient. By subjecting the mixture to an electrical field, the water molecules will carry the uncharged particles with them as they flow from one pole towards the other.
Typically the technique for developing the electric field in iontophoresis or iontohydrokinesis involves placing both positive and negative electrodes externally of the patient's body or the specific organ that is to be treated. Consequently, the techniques do not lend themselves to targeted, localized treatment of internal body organs.
Generally, when it has been desired to use the procedure locally on an internal organ, it has been necessary to expose the organ surgically. Once the organ is exposed, the electrodes can be placed on opposite sides of the organ, as in the case of the delivery of procainamide to the heart during open chest surgery, discussed above. Such a surgical technique for localized treatment of internal organs has obvious drawbacks such as trauma to the patient and other disadvantages and risks of general surgery. It would be desirable, therefore, to provide a less invasive technique for delivering an effective concentration of medication locally to an internal organ. For example, it would be desirable to deliver concentrations of selected compounds to the wall of an artery as an adjunct to angioplasty, a procedure to enlarge a narrowed (stenosed) portion of an artery by placing a balloon in the stenosis and inflating the balloon to dilate the stenosis, thus improving blood flow through the artery.
A significant problem in angioplasty is the relatively high rate of restenosis (approximately 30%) after performinq an initial anqioplasty. It has been suggested that restenosis may be controlled or possibly prevented by applying suitable medication to the wall of the artery in the region of the angioplasty. For example, among the factors thought to contribute to incidence of restenosis is the uncontrolled proliferation of smooth muscle cells in the arterial wall, as a consequence of the angioplasty. To that end, it has been proposed that a concentrated dose of suitable medication, such as heparin, be applied to a local region of an artery and forced into the wall of the artery under pressure. A catheter adopted for that purpose is disclosed in U.S. Pat. No. 4,636,195 issued Jan. 13, 1987 to Wolinsky. The Wolinsky patent describes a catheter having a pair of spaced balloons mounted on the distal end of the catheter. The catheter is inserted into the patient's arteries and is navigated to the site of the angioplasty. The catheter is positioned so that the balloons embrace the region of the angioplasty. Suitable medication, such as heparin, then is forced, under pressure, into the space between the inflated balloons to force the medication, under pressure, into the wall of the artery.
It is among the objects of the invention, therefore, to provide a minimally evasive technique for delivering an effective concentration of medication or the like locally to an internal organ of the patient.